1. Field of the Invention
The invention concerns a method for impregnating a flat, fibrous substrate penetrated by a fluid synthetic resin of low viscosity, products made using this method and apparatus with which to carry out the method.
2. Discussion of the Prior Art
It is known to lower the viscosity of the resin to be deposited on a substrate to achieve adequate impregnation. Illustratively this is done by adding solvents such as water or alcohols. When using paper, the addition of water to the resin mixture causes swelling of the substrate. The large amount of solvent required for swelling must be evaporated following impregnation; this condition requires substantial transit times in the drier and as a result limits on the capacity of the impregnating device.
It is further known from the Japanese patent document A 59-042923 to avoid an increase in viscosity during impregnation by preventing solvent evaporation from the bath by means of a cover. The substrate to be impregnated is guided by a scoop roller dipping into the bath and thereupon it is returned by direction-changing rollers into the resin bath.